Women with increased levels of Müllerian inhibiting substance (MIS), best known for regulating in utero sexual differentiation in boys, may be at a greater risk for breast cancer, according to a new study published online October 9 in the .

To determine whether MIS levels were associated with breast cancer risk, Joanne F. Dorgan, Ph.D., MPH, of the Fox Chase Cancer Center in Philadelphia, and colleagues conducted a prospective case-control study of 309 participants who were registered in the Columbia, Missouri Serum Bank. Blood samples were donated by women with in situ or invasive breast cancer who, at the time of donation, were free of cancer. Each of 105 breast cancer patients was matched to two control subjects. MIS was measured in serum using an enzyme-linked immunosorbent assay.

Researchers found that increasing MIS serum concentrations were associated with increased breast cancer risk in this population.

"Additional research is needed, including confirmatory epidemiological studies on the association of serum MIS with breast cancer and studies aimed at identifying the biological mechanism underlying the association," the authors write.